Moisture Control | Roof Decks | Rigid Insulation | Roof Membranes

 

ROOF MEMBRANES

Base Sheet Installations
The base sheet layer shall be started at the lowest point of the roof deck such as at a drain or downslope perimeter edge. Base sheet side laps shall be a minimum of 2”, leaving an exposure of 34” for 36” wide base sheets and 38” for 40” wide base sheets.

Installation of Base Sheets
Install 1 layer of base sheets, adhering the base sheets to the substrate, except when installing the base sheets directly to nailable type decks, which require mechanically fastened base sheets. Adhere an extra layer of base sheets in valleys and waterways prior to installation of the ply sheets. Extend the extra layer of base sheets a minimum of 12” up inclines.

Nailing Pattern for Mechanically Fastened Base Sheets
To mechanically fasten the base sheet, nail the seams and ends 9” on center. Also, stagger nail two rows 18” on center and 12” distant from each edge.

Ply Sheet Installations
4 Shingled Layers of 40” Wide Ply Sheets
To install 4 shingled layers of 40” wide ply sheets, make and install the starter sheets from ply sheets cut into the following widths: 10”, 20”, and 30”. Align the finished edge of each layer of starter sheets over the outside edge of the base sheets. Start with the narrowest starter sheet and continue by installing the next widest sheet for each layer of starter sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 32.00” over the first full width layer of ply sheets, leaving 8.00” exposed: Thereafter, lap the ply sheets 30.50”, leaving 9.50” exposed.

3 Shingled Layers of 40” Wide Ply Sheets
To install 3 shingled layers of 40” wide ply sheets, make and install the starter sheets from ply sheets cut into the following widths: 13.33” and 26.67”. Align the finished edge of each layer of starter sheets over the outside edge of the base sheets. Start with the narrowest starter sheet and continue by installing the next widest sheet for each layer of starter sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 28.65” over the first full width layer of ply sheets, leaving 11.35” exposed: Thereafter, lap the ply sheets 27.40”, leaving 12.60” exposed.

2 Shingled Layers of 40” Wide Ply Sheets
To install 2 shingled layers of 40” wide ply sheets, make and install the starter sheets from ply sheets cut into 20” widths. Align the finished edge of the starter sheets over the outside edge of the base sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 22.00” over the first full width layer of ply sheets, leaving 18.00” exposed: Thereafter, lap the ply sheets 21.00”, leaving 19.00” exposed.

4 Shingled Layers of 36” Wide Ply Sheets
To install 4 shingled layers of 36” wide ply sheets, make and install the starter sheets from ply sheets cut into the following widths: 9”, 18”, and 27”. Align the finished edge of each layer of starter sheets over the outside edge of the base sheets. Start with the narrowest starter sheet and continue by installing the next widest sheet for each layer of starter sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 29.00” over the first full width layer of ply sheets, leaving 7.00” exposed: Thereafter, lap the ply sheets 27.50”, leaving 8.50” exposed.

3 Shingled Layers of 36” Wide Ply Sheets
To install 3 shingled layers of 36” wide ply sheets, make and install the starter sheets from ply sheets cut into the following widths: 12” and 24”. Align the finished edge of each layer of starter sheets over the outside edge of the base sheets. Start with the narrowest starter sheet and continue by installing the next widest sheet for each layer of starter sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 26.00” over the first full width layer of ply sheets, leaving 10.00” exposed: Thereafter, lap the ply sheets 24.75”, leaving 11.25” exposed.

2 Shingled Layers of 36” Wide Ply Sheets
To install 2 shingled layers of 36” wide ply sheets, make and install the starter sheets from ply sheets cut into 18” widths. Align the finished edge of the starter sheets over the outside edge of the base sheets. Install the first layer of full width ply sheets over the starter sheets, aligning the edge of the ply sheets over the outside edge of the starter sheets. Lap the second layer of full width ply sheets 20.00” over the first full width layer of ply sheets, leaving 16.00” exposed: Thereafter, lap the ply sheets 19.00”, leaving 17.00” exposed.

1 Layer of 40” Ply Sheets
To install 1 layer of 40” wide ply sheets, make and install the starter sheets from the ply sheets cut into 20” widths. Align the finished edge of the starter sheets over the outside edge of the base sheets. Continue by installing full width ply sheets. Side laps shall be a minimum of 2”, leaving an exposure of 38”. Keep the seams of the ply sheets offset a minimum of 6” from the seams of base sheets.

1 Layer of 36” Ply Sheets
To install 1 layer of 36” wide ply sheets, make and install the starter sheets from the ply sheets cut into 18” widths. Align the finished edge of the starter sheets over the outside edge of the base sheets. Continue by installing full width ply sheets. Side laps shall be a minimum of 2”, leaving an exposure of 34”. Keep the seams of the ply sheets offset a minimum of 6” from the seams of base sheets.